High-brightness laser-based White light sources for automotive lighting applications (Conference Presentation)

Modern vehicle lighting systems are intended to improve safety on the road by providing the adequate visibility to the drivers under different driving conditions from within a compact housing. Using a high-power semipolar GaN-based blue laser diode (>3W) that pumps a yellow phosphor in a remote position, BMW and SLD co-developed a new high-luminance white point-like source having a peak brightness of over 1000 cd/mm², which is 10 times than that of high-power white LEDs. This results in extending the range of the visibility to the maximum regulatory photometric values (~600m) and in enhancing the contrast of different light distributions in the far-field. New lighting functions, devoted to guiding, assistance and communication, for example between self-driving vehicles and pedestrians, require variable, free patterned light distributions that are clearly perceivable by the driver and/or pedestrians. One way to achieve them is through the use of high-luminance, dynamic light sources with a higher luminous flux and a higher “automotive” lifetime. Such sources should enable a relatively high resolution in the far-field. Multiple efficient, high-power semi-polar blue laser emitters have therefore to be integrated in a thermo-optically stable package. Different patterns are generated on an optimized structured phosphor that is excited by a moving blue laser spot. This dynamic is enabled by a robust, compact, fast beam steering MEMS mirror. The pattern is projected in the far-field using a customized secondary optical system. Eye safety measures that ensure a safe usage in the vehicle and in the manufacturing sites, have to be implemented in such sources.